2014-01-29 Convert an equation into a PNG image
I recently faced an issue while converting an equation into an image using the method I developped in this post. I do not know why but the following expression \frac{X_t}{Y_t} did not work. So I had to use miktex and more specifically htlatex through the following command line:
htlatex eq.tex html "" "" "--interaction=nonstopmode"
The last parameter avoids the programm to check the input stream if an error was detected. I wrapped this into a quick and dirty python program you can find below. It will also describe what eq.tex should contain.
import os, shutil, sys
from pyquickhelper import run_cmd
def convert_short_latex_into_png(latex, temp_folder = ".", fLOG = print,
miktex = r"C:\Program Files\MiKTeX 2.9\miktex\bin\x64",
final_name = None) :
"""
Convert a short latex script into an image.
@param latex latex equation
@param temp_folder temp_folder (where temporary files will be placed)
@param fLOG logging function
@param miktex miktex location
@param final_name if not None, copy the image at this location using this name
@return a location to the image (it should be copied)
You should not call the function twice at the same in the same folder.
@warning The function ends the program if there was a failure. Something is missing on the command line.
"""
if not os.path.exists(miktex) :
raise FileNotFoundError("unable to find miktex")
if sys.platform.startswith("win") :
htlatex = os.path.join(miktex,"htlatex.exe")
if not os.path.exists(htlatex) :
raise FileNotFoundError("unable to find htlatex")
else :
htlatex = os.path.join(miktex,"htlatex")
if not os.path.exists(temp_folder) :
os.makedirs(temp_folder)
eq = os.path.join(temp_folder, "eq.tex")
with open(eq, "w") as f :
f.write(r"""\documentclass[12pt]{article}
\pagestyle{empty}
\begin{document}
$$
%s
$$
\end{document}""".replace(" ","")%latex.strip("\n\r "))
cmd = htlatex + ' eq.tex html "" "" "--interaction=nonstopmode"'
cwd = os.getcwd() ;
os.chdir(temp_folder)
out,err =run_cmd(cmd, wait=True)
os.chdir(cwd)
if "FAILED" in err :
raise Exception("it failed\n-----\n{0}\n----------\n{1}".format(out,err))
img = os.path.join(temp_folder,"eq0x.png")
if not os.path.exists(img):
with open(os.path.join(temp_folder,"eq.log"),"r") as f :
log = f.read()
raise FileNotFoundError("the compilation did not work\n" + log)
if final_name != None :
shutil.copy(img, final_name)
return final_name
else :
return img
The function run_cmd comes from module pyquickhelper. It calls a process using subprocess.Popen.
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Xavier Dupré
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